42 research outputs found
Epilepsy
With the vision of including authors from different parts of the world, different educational backgrounds, and offering open-access to their published work, InTech proudly presents the latest edited book in epilepsy research, Epilepsy: Histological, electroencephalographic, and psychological aspects. Here are twelve interesting and inspiring chapters dealing with basic molecular and cellular mechanisms underlying epileptic seizures, electroencephalographic findings, and neuropsychological, psychological, and psychiatric aspects of epileptic seizures, but non-epileptic as well
An overview of deep learning techniques for epileptic seizures detection and prediction based on neuroimaging modalities: Methods, challenges, and future works
Epilepsy is a disorder of the brain denoted by frequent seizures. The symptoms of seizure include confusion,
abnormal staring, and rapid, sudden, and uncontrollable hand movements. Epileptic seizure detection methods
involve neurological exams, blood tests, neuropsychological tests, and neuroimaging modalities. Among these,
neuroimaging modalities have received considerable attention from specialist physicians. One method to facilitate
the accurate and fast diagnosis of epileptic seizures is to employ computer-aided diagnosis systems (CADS)
based on deep learning (DL) and neuroimaging modalities. This paper has studied a comprehensive overview of
DL methods employed for epileptic seizures detection and prediction using neuroimaging modalities. First, DLbased
CADS for epileptic seizures detection and prediction using neuroimaging modalities are discussed. Also,
descriptions of various datasets, preprocessing algorithms, and DL models which have been used for epileptic
seizures detection and prediction have been included. Then, research on rehabilitation tools has been presented,
which contains brain-computer interface (BCI), cloud computing, internet of things (IoT), hardware implementation
of DL techniques on field-programmable gate array (FPGA), etc. In the discussion section, a comparison
has been carried out between research on epileptic seizure detection and prediction. The challenges in
epileptic seizures detection and prediction using neuroimaging modalities and DL models have been described. In
addition, possible directions for future works in this field, specifically for solving challenges in datasets, DL,
rehabilitation, and hardware models, have been proposed. The final section is dedicated to the conclusion which
summarizes the significant findings of the paper
Artifact Removal Methods in EEG Recordings: A Review
To obtain the correct analysis of electroencephalogram (EEG) signals, non-physiological and physiological artifacts should be removed from EEG signals. This study aims to give an overview on the existing methodology for removing physiological artifacts, e.g., ocular, cardiac, and muscle artifacts. The datasets, simulation platforms, and performance measures of artifact removal methods in previous related research are summarized. The advantages and disadvantages of each technique are discussed, including regression method, filtering method, blind source separation (BSS), wavelet transform (WT), empirical mode decomposition (EMD), singular spectrum analysis (SSA), and independent vector analysis (IVA). Also, the applications of hybrid approaches are presented, including discrete wavelet transform - adaptive filtering method (DWT-AFM), DWT-BSS, EMD-BSS, singular spectrum analysis - adaptive noise canceler (SSA-ANC), SSA-BSS, and EMD-IVA. Finally, a comparative analysis for these existing methods is provided based on their performance and merits. The result shows that hybrid methods can remove the artifacts more effectively than individual methods
UNSUPERVISED CLASSIFICATION OF HIGH-FREQUENCY OSCILLATIONS IN NEOCORTICAL EPILEPSY AND CONTROL PATIENTS
Quality of life for the more than 15 million people with drug-resistant epilepsy is tied to how precisely the brain areas responsible for generating their seizures can be localized. High-frequency (100-500 Hz) field-potential oscillations (HFOs) are emerging as a candidate biomarker for epileptogenic networks, but quantitative HFO studies are hampered by selection bias arising out of the need to reduce large volumes of data in the absence of capable automated processing methods. In this thesis, I introduce and evaluate an algorithm for the automatic detection and classification of HFOs that can be deployed without human intervention across long, continuous data records from large numbers of patients. I then use the algorithm in analyzing unique macro- and microelectrode intracranial electroencephalographic recordings from human neocortical epilepsy patients and controls. A central finding is that one class of HFOs discovered by the algorithm (median bandpassed spectral centroid ~140 Hz) is more prevalent in the seizure onset zone than outside. The outcomes of this work add to our understanding of epileptogenic networks and are suitable for near-term translation into improved surgical and device-based treatments
Neural Anomalies Monitoring: Applications to Epileptic Seizure Detection and Prediction
There
have
been
numerous
efforts
in
the
field
of
electronics
with
the
aim
of
merging
the
areas
of
healthcare
and
technology
in
the
form
of
low
power,
more
efficient
hardware.
However
one
area
of
development
that
can
aid
in
the
bridge
of
healthcare
and
emerging
technology
is
in
Information
and
Communication
Technology
(ICT).
Here,
databasing
and
analysis
systems
can
help
bridge
the
wealth
of
information
available
(blood
tests,
genetic
information,
neural
data)
into
a
common
framework
of
analysis.
Also,
ICT
systems
can
integrate
real-time
processing
from
emerging
technological
solutions,
such
as
developed
low-power
electronics.
This
work
is
based
on
this
idea,
merging
technological
solutions
in
the
form
of
ICT
with
the
need
in
healthcare
to
identify
normality
in
a
patients’
health
profile.
In
this
work
we
develop
this
idea
and
explain
the
concept
more
thoroughly.
We
then
go
on
to
explore
two
applications
under
development.
The
first
is
a
system
designed
around
monitoring
neural
activity
and
identifying,
through
a
processing
algorithm,
what
is
normal
activity,
such
that
we
can
identify
anomalies,
or
abnormalities
in
the
signal.
We
explore
Epilespy
with
seizure
detection
and
prediction
as
an
application
case
study
to
show
the
potential
of
this
method.
The
motivation
being
that
current
methods
of
prediction
have
proven
to
be
unsuccessful.
We
show
that
using
our
algorithm
we
can
achieve
significant
success
in
seizure
prediction
and
detection,
above
and
beyond
current
methods.
The
second
application
explores
the
link
between
genetic
information
and
standard
tests
(blood,
urine
etc...)
and
how
they
link
in
together
to
define
a
personalised
benchmark.
We
show
how
this
could
work
and
the
steps
that
have
been
made
towards
developing
such
a
database
Intraoperative Guidance for Pediatric Brain Surgery based on Optical Techniques
For most of the patients with brain tumors and/or epilepsy, surgical resection of brain lesions, when applicable, remains one of the optimal treatment options. The success of the surgery hinges on accurate demarcation of neoplastic and epileptogenic brain tissue. The primary goal of this PhD dissertation is to demonstrate the feasibility of using various optical techniques in conjunction with sophisticated signal processing algorithms to differentiate brain tumor and epileptogenic cortex from normal brain tissue intraoperatively.
In this dissertation, a new tissue differentiation algorithm was developed to detect brain tumors in vivo using a probe-based diffuse reflectance spectroscopy system. The system as well as the algorithm were validated experimentally on 20 pediatric patients undergoing brain tumor surgery at Nicklaus Children’s Hospital. Based on the three indicative parameters, which reflect hemodynamic and structural characteristics, the new algorithm was able to differentiate brain tumors from the normal brain with a very high accuracy.
The main drawbacks of the probe-based system were its high susceptibility to artifacts induced by hand motion and its interference to the surgical procedure. Therefore, a new optical measurement scheme and its companion spectral interpretation algorithm were devised. The new measurement scheme was evaluated both theoretically with Monte Carlo simulation and experimentally using optical phantoms, which confirms the system is capable of consistently acquiring total diffuse reflectance spectra and accurately converting them to the ratio of reduced scattering coefficient to absorption coefficient (µs’(λ)/µa(λ)). The spectral interpretation algorithm for µs’(λ)/µa(λ) was also validated based on Monte Carlo simulation. In addition, it has been demonstrated that the new measurement scheme and the spectral interpretation algorithm together are capable of detecting significant hemodynamic and scattering variations from the Wistar rats’ somatosensory cortex under forepaw stimulation.
Finally, the feasibility of using dynamic intrinsic optical imaging to distinguish epileptogenic and normal cortex was validated in an in vivo study involving 11 pediatric patients with intractable epilepsy. Novel data analysis methods were devised and applied to the data from the study; identification of the epileptogenic cortex was achieved with a high accuracy
EpiGauss : caracterização espacio-temporal da actividade cerebral em epilepsia
Doutoramento em Engenharia ElectrotĂ©cnicaA epilepsia Ă© uma patologia cerebral que afecta cerca de 0,5% da população mundial. Nas epilepsias focais, o principal objectivo clĂnico Ă© a localização da zona epileptogĂ©nica (área responsável pelas crises), uma informação crucial para uma terapĂŞutica adequada. Esta tese Ă© centrada na caracterização da actividade cerebral electromagnĂ©tica do cĂ©rebro epilĂ©ptico. As contribuições nesta área, entre a engenharia e neurologia clĂnica, sĂŁo em duas direcções. Primeiro, mostramos que os conceitos associados Ă s pontas podem ser imprecisos e nĂŁo ter uma definição objectiva, tornando necessária uma reformulação de forma a definir uma referĂŞncia fiável em estudos relacionados com a análise de pontas. Mostramos que as caracterĂsticas das pontas em EEG sĂŁo estatisticamente diferentes das pontas em MEG. Esta constatação leva a concluir que a falta de objectividade na definição de ponta na literatura pode induzir utilizações erradas de conceitos associados ao EEG na análise de MEG. TambĂ©m verificamos que o uso de conjuntos de detecções de pontas efectuadas por especialistas (MESS) como referĂŞncia pode fornecer resultados enganadores quando apenas baseado em critĂ©rios de consenso clĂnico, nomeadamente na avaliação da sensibilidade e especificidade de mĂ©todos computorizados de detecção de pontas Em segundo lugar, propomos o uso de mĂ©todos estatĂsticos para ultrapassar a falta de precisĂŁo e objectividade das definições relacionadas com pontas. Propomos um novo mĂ©todo de neuroimagem suportado na caracterização de geradores electromagnĂ©ticos – EpiGauss – baseado na análise individual dos geradores de eventos do EEG que explora as suas estruturas espacio-temporais atravĂ©s da análise de “clusters”. A aplicação de análise de “clusters” Ă análise geradores de eventos do EEG tem como objectivo usar um mĂ©todo nĂŁo supervisionado, para encontrar estruturas espacio-temporais dps geradores relevantes. Este mĂ©todo, como processo nĂŁo supervisionado, Ă© orientado a utilizadores clĂnicos e apresenta os resultados sob forma de imagens mĂ©dicas com interpretação similar a outras tĂ©cnicas de imagiologia cerebral. Com o EpiGauss, o utilizador pode determinar a localização estatisticamente mais provável de geradores, a sua estabilidade espacial e possĂveis propagações entre diferente áreas do cĂ©rebro. O mĂ©todo foi testado em dois estudos clĂnicos envolvendo doentes com epilepsia associada aos hamartomas hipotalâmicos e o outro com doentes com diagnĂłstico de epilepsia occipital. Em ambos os estudos, o EpiGauss foi capaz de identificar a zona epileptogĂ©nica clĂnica, de forma consistente com a histĂłria e avaliação clĂnica dos neurofisiologistas, fornecendo mais informação relativa Ă estabilidade dos geradores e possĂveis percursos de propagação da actividade epileptogĂ©nica contribuindo para uma melhor caracterização clĂnica dos doentes. A conclusĂŁo principal desta tese Ă© que o uso de tĂ©cnicas nĂŁo supervisionadas, como a análise de “clusters”, associadas as tĂ©cnicas nĂŁo-invasivas de EMSI, pode contribuir com um valor acrescido no processo de diagnĂłstico clĂnico ao fornecer uma caracterização objectiva e representação visual de padrões complexos espaciotemporais da actividade elĂ©ctrica epileptogĂ©nica.Epilepsy is a brain pathology that affects 0.5% of the world population. In focal epilepsies, the main clinical objective is the localization of the epileptogenic zone (brain area responsible for the epileptic seizures – EZ), a key information to decide an adequate therapeutic approach. This thesis is centred on electromagnetic activity characterization of the epileptic brain. Our contribution to this boundary area between engineering and clinical neurology is two-folded. First we show that spike related clinical concepts can be unprecise and some do not have objective definitions making necessary a reformulation in order to have a reliable reference in spike related studies. We show that EEG spike wave quantitative features are statistically different from their MEG counterparts. This finding leads to the conclusion that the lack of objective spike feature definitions in the literature can induce the wrong usage of EEG feature definition in MEG analysis. We also show that the use of multi-expert spike selections sets (MESS) as gold standard, although clinically useful, may be misleading whenever defined solely in terms of clinical agreement criteria, namely as references for automatic spike detection algorithms in sensitivity and specificity method analysis. Second, we propose the use of statistical methods to overcome some lack of precision and objectivity in spike related definitions. In this context, we propose a new ElectroMagnetic Source Imaging (EMSI) method – EpiGauss – based on cluster analysis that explores both spatial and temporal information contained in individual events sources analysis characterisation. This automatic cluster method for the analysis of spike related electric generators based in EEG is used to provide an unsupervised tool to find their relevant spatio-temporal structures. This method enables a simple unsupervised procedure aimed for clinical users and presents its results in an intuitive representation similar to other brain imaging techniques. With EpiGauss, the user is able to determine statistically probable source locations, their spatial stability and propagation patterns between different brain areas. The method was tested in two different clinical neurophysiology studies, one with a group of Hypothalamic Hamartomas and another with a group of Occipital Epilepsy patients. In both studies EpiGauss identified the clinical epileptogenic zone, consistent with the clinical background and evaluation of neurophysiologists, providing further information on stability of source locations and their probable propagation pathways that enlarges their clinical interpretation. This thesis main conclusion is that the use of unsupervised techniques, such as clustering, associated with EMSI non-invasive techniques, can bring an added value in clinical diagnosis process by providing objective and visual representation of complex epileptic brain spatio-temporal activity patterns
Automatic Detection and Classification of Neural Signals in Epilepsy
The success of an epilepsy treatment, such as resective surgery, relies heavily on the accurate identification and localization of the brain regions involved in epilepsy for which patients undergo continuous intracranial electroencephalogram (EEG) monitoring. The prolonged EEG recordings are screened for two main biomarkers of epilepsy: seizures and interictal spikes. Visual screening and quantitation of these two biomarkers in voluminous EEG recordings is highly subjective, labor-intensive, tiresome and expensive. This thesis focuses on developing new techniques to detect and classify these events in the EEG to aid the review of prolonged intracranial EEG recordings.
It has been observed in the literature that reliable seizure detection can be made by quantifying the evolution of seizure EEG waveforms. This thesis presents three new computationally simple non-patient-specific (NPS) seizure detection systems that quantify the temporal evolution of seizure EEG. The first method is based on the frequency-weighted-energy, the second method on quantifying the EEG waveform sharpness, while the third method mimics EEG experts. The performance of these new methods is compared with that of three state-of-the-art NPS seizure detection systems. The results show that the proposed systems outperform these state-of-the-art systems.
Epilepsy therapies are individualized for numerous reasons, and patient-specific (PS) seizure detection techniques are needed not only in the pre-surgical evaluation of prolonged EEG recordings, but also in the emerging neuro-responsive therapies. This thesis proposes a new model-based PS seizure detection system that requires only the knowledge of a template seizure pattern to derive the seizure model consisting of a set of basis functions necessary to utilize the statistically optimal null filters (SONF) for the detection of the subsequent seizures. The results of the performance evaluation show that the proposed system provides improved results compared to the clinically-used PS system.
Quantitative analysis of the second biomarker, interictal spikes, may help in the understanding of epileptogenesis, and to identify new epileptic biomarkers and new therapies. However, such an analysis is still done manually in most of the epilepsy centers. This thesis presents an unsupervised spike sorting system that does not require a priori knowledge of the complete spike data